This study investigates public perceptions of AI conversational agents (CAs) across two cultures, the United States and China, using computational methods to analyze one million social media discussions. The research reveals significant cultural differences in how people perceive CAs. Chinese participants tended to view CAs hedonically, perceiving voice-based and physically embodied CAs as warmer and more competent, and generally expressed positive emotions. In contrast, US participants saw CAs more functionally, with an ambivalent attitude. Warm perception was a key driver of positive emotions toward CAs in both countries. The study also explores how technical characteristics of CAs influence public perceptions, including conversational focus, conversational mode, human-like appearance, and physical embodiment. The findings suggest that cultural values and technical features interact to shape how CAs are perceived and valued by the public. The study recommends designing CAs that are more contextually sensitive and user-centric to better meet users' needs and preferences. The research contributes insights into how culture and other structural factors shape public perceptions of CAs in terms of warmth, competence, and emotional valence, and provides a framework for understanding the interplay between external structural factors and inherent technical characteristics in shaping public perceptions of CAs. The study also highlights the importance of considering cultural differences when designing CAs to enhance user experience and acceptance.This study investigates public perceptions of AI conversational agents (CAs) across two cultures, the United States and China, using computational methods to analyze one million social media discussions. The research reveals significant cultural differences in how people perceive CAs. Chinese participants tended to view CAs hedonically, perceiving voice-based and physically embodied CAs as warmer and more competent, and generally expressed positive emotions. In contrast, US participants saw CAs more functionally, with an ambivalent attitude. Warm perception was a key driver of positive emotions toward CAs in both countries. The study also explores how technical characteristics of CAs influence public perceptions, including conversational focus, conversational mode, human-like appearance, and physical embodiment. The findings suggest that cultural values and technical features interact to shape how CAs are perceived and valued by the public. The study recommends designing CAs that are more contextually sensitive and user-centric to better meet users' needs and preferences. The research contributes insights into how culture and other structural factors shape public perceptions of CAs in terms of warmth, competence, and emotional valence, and provides a framework for understanding the interplay between external structural factors and inherent technical characteristics in shaping public perceptions of CAs. The study also highlights the importance of considering cultural differences when designing CAs to enhance user experience and acceptance.